The types and detailed introduction of universal testing machines on the market

There are two main types of universal testing machines currently on the market, four types:

1. Hydraulic series: manual hydraulic universal testing machine, electro-hydraulic servo hydraulic universal testing machine

2. Electronic universal series: conventional electronic universal testing machine, high-performance electronic universal testing machine.

Performance characteristics of various categories

1.Hydraulic universal testing machine series:

1: The manual hydraulic universal material testing machine mainly uses simple high-pressure oil source as the power source, manual adjustment valve as the control element, and manually load it. Therefore, it belongs to the open-loop control system. Due to the limitations of the oil source flow rate and main engine structure, its cylinder piston stroke is smaller, the common one is generally around 300mm, and its test speed is generally smaller.

Affected by price factors, pressure sensors generally use pressure sensors (large tonnages basically use pressure sensors). Therefore, the accuracy is lower and the range is smaller. Generally, the accuracy is level 1 or level 2, and the range is generally 4%-100% F.S. Affected by the friction of the oil cylinder, it is generally difficult to achieve a very small tonnage, and the smallest in China is 5T. However, due to its unique low price and large tonnage characteristics, it is still widely used in finished product inspection and single material index testing.

2: The electro-hydraulic servo universal testing machine mainly uses precision high-pressure oil source as the power source, and uses servo valves or proportional valves as control elements for closed-loop automatic control, so the control performance is high, and three control modes can be realized: load, strain, and displacement. Like the manual hydraulic universal material testing machine, the electro-hydraulic servo universal testing machine is limited by the oil source flow rate, and its test speed is relatively low.

Due to the use of closed-loop automatic control, system stiffness has become the key to the normal operation of the entire system. As we all know, the stiffness of liquid is relatively low. In order to minimize the impact of liquid on the rigidity of the whole machine, the stroke of the electro-hydraulic servo tester is not large. Also affected by the rigidity of the whole machine, the tonnage of the electro-hydraulic servo tester cannot be very small, basically more than one ton. However, because it has multiple control modes, it has the characteristics of flexible use and high performance.

2.Electronic universal testing machine series:

1: Conventional electronic/universal testing machine. It mainly uses servo motors as power sources, and lead screws and wire masters as execution components to realize the speed control of the moving beam of the test machine. Its test speed range can be adjusted. Taking RGM-200 as an example, its test speed can reach 0.001mm/min-1000mm/min, the speed ratio can reach 1 million times, and the test stroke can be determined according to needs, reaching several meters.

This cannot be achieved by hydraulic testing machines anyway. With the development of electronic technology and the improvement of servo motor performance, the motors used in electronic universal testing machines have been used from the early DC servo motors to the current ones that use more AC servo motors.

From the early power components to the use of thyristor for phase shift trigger control to the use of a variety of power modules to achieve pulse width modulation control, the performance of electronic universal has made a qualitative leap. In people's mind, the electronic universal failure rate is high, and the poor performance is no longer there. Since conventional electronic universal adopts speed control, the system stiffness is not high, which creates favorable conditions for the realization of small tonnage test machines. Judging from the current international and domestic situation, universal testing machines below one ton are basically conventional electronic universal testing machines. It has a wide range of uses and cost-effectiveness.

2: The high-performance electronic universal testing machine is the same as the conventional universal testing machine. It also uses a servo motor as the power source, and the lead screw and wire master as the execution parts. The difference between it and the conventional electronic universal testing machine is that its control method can be load control, strain control or displacement control.

In addition to the characteristics of conventional electronic universal versatile speed and large stroke, it also has all the advantages of electro-hydraulic servo testing machines, so it is a universal material testing machine with current performance. At present, the best of this type of test machine basically uses the EDC 120 series produced by Germany's Doli company as the core control component. Of course, this type of universal testing machine also has its disadvantages. Because it has three control modes: load, strain, and displacement, the stability of the whole machine is directly related to the stiffness of the system, and the stiffness of the sample directly affects the stiffness of the system.

Therefore, when there are many types of test samples, the stiffness of the whole machine will change greatly, so it is difficult to ensure that all tests can be carried out normally. In order to meet the normal performance of all tests, the parameters of the control system (P, I, D parameters) need to be adjusted at any time. This is difficult for non-automatic control professionals, so that the advantages of this type of test machine cannot be fully utilized, and the price of this type of test machine is relatively high.